A fire balloon(風船爆弾,fūsen bakudan, lit. "balloon bomb"), or Fu-Go(ふ号[兵器],fugō [heiki], lit. "Code Fu [Weapon]"), was a weapon launched by Japan during World War II. A hydrogenballoon with a load varying from a 15 kg (33 lb) antipersonnel bomb to one 12-kilogram (26 lb) incendiary bomb and four 5 kg (11 lb) incendiary devices attached, it was designed as a cheap weapon intended to make use of the jet stream over the Pacific Ocean and drop bombs on American and Canadian cities, forests, and farmland.[1][2]

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From late 1944 until early 1945, the Japanese launched over 9,300 fire balloons, of which 300 were found or observed in the U.S. Despite the high hopes of their designers, the balloons were ineffective as weapons, causing only six deaths (from one single incident) and a small amount of damage.

"Type B" rubberized silk balloon, recovered at sea and reinflated. Outline of a human is provided for scale.

The Japanese designed two types of balloons. The first was called the "Type B Balloon" and was designed by the Japanese Navy. It was 9 m (30 ft) in diameter and consisted of rubberized silk. The type B balloons were sent first and mainly used for meteorological purposes. The Japanese used them to determine the possibility of the bomb-carrying balloons reaching North America.[6] The second type was the bomb-carrying balloon. Japanese bomb-carrying balloons were 10 m (33 ft) in diameter and, when fully inflated, held about 540 m3 (19,000 cu ft) of hydrogen. Their launch sites were located on the east coast of the main Japanese island of Honshū.

General Kusaba's men launched over 9,000 balloons throughout the course of the project. The Japanese expected 10% (around 900) of them to reach America, which is also what is currently believed by researchers.[9] About 300 balloon bombs were found or observed in America. It is likely that more balloon bombs landed in unpopulated areas of North America.

The balloon campaign was the fourth attack the Japanese had made on the American mainland. The fūsen bakudan campaign was, however, the most earnest of the attacks. The concept was the brainchild of the Imperial Japanese Army's Ninth Army's Number Nine Research Laboratory, under Major General Sueyoshi Kusaba, with work performed by Technical Major Teiji Takada and his colleagues. The balloons were intended to make use of a strong current of winter air that the Japanese had discovered flowing at high altitude and speed over their country, which later became known as the jet stream.[10]

The jet stream reported by Wasaburo Oishi[11] blew at altitudes above 9.15 km (30,000 ft) and could carry a large balloon across the Pacific in three days, over a distance of more than 8,000 kilometers (5,000 mi). Such balloons could carry incendiary and high-explosive bombs to the United States and drop them there to kill people, destroy buildings, and start forest fires.[10]

Minimum altitude control, using a master aneroid (center) with several redundant backups.

The preparations were lengthy because the technological problems were acute. A hydrogen balloon expands when warmed by the sunlight, and rises; then it contracts when cooled at night, and falls. The engineers devised a control system driven by an altimeter to discard ballast. When the balloon descended below 9 km (30,000 ft), it electrically fired a charge to cut loose sandbags. The sandbags were carried on a cast-aluminium four-spoked wheel and discarded two at a time to keep the wheel balanced.[10]

Similarly, when the balloon rose above about 11.6 km (38,000 ft), the altimeter activated a valve to vent hydrogen. The hydrogen was also vented if the balloon's pressure reached a critical level.[10]

The control system ran the balloon through three days of flight. At that time, it was likely over the U.S., and its ballast was expended. The final flash of gunpowder released the bombs, also carried on the wheel, and lit a 19.5 meters (64 feet) long fuse that hung from the balloon's equator. After 84 minutes, the fuse fired a flash bomb that destroyed the balloon.[10]

Still from a movie showing ballast release.

The balloon had to carry about 454 kilograms (1,001 lb) of gear. At first the balloons were made of conventional rubberized silk, but improved envelopes had less leakage. An order went out for ten thousand balloons made of "washi", a paper derived from mulberry bushes that was impermeable and very tough. It was only available in squares about the size of a road map, so it was glued together in three or four laminations using edible konnyaku (devil's tongue) paste – though hungry workers stealing the paste for food created some issues. Many workers were nimble-fingered teenaged school girls.[12] They assembled the paper in many parts of Japan. Large indoor spaces, such as sumo halls, sound stages, and theatres, were required for the envelope assembly.[10]

The Japanese Imperial Army Noborito Institute cultivated anthrax and pasteurella pestis, furthermore, it produced enough cowpox viruses to infect the whole United States.[14] The plan of deployment of these biological weapon on fire balloons was planned in 1944.[15] The Emperor Hirohito did not admit deployment of biological weapons on the occasion of a report of President Staff Officer Umezu on October 25, 1944. Consequently, the biological warfare was not realized.[16]

Similar, but cruder, balloons were also used by Britain to attack Germany between 1942 and 1944.

A balloon launch organization of three battalions was formed. The first battalion included headquarters and three squadrons totaling 1,500 men in Ibaraki Prefecture with nine launch stations at Ōtsu. The second battalion of 700 men in three squadrons operated six launch stations at Ichinomiya, Chiba; and the third battalion of 600 men in two squadrons operated six launch stations at Nakoso in Fukushima Prefecture. The Ōtsu site included hydrogen gas generating facilities; but the 2nd and 3rd battalion launch sites used hydrogen manufactured elsewhere. The best time to launch was just after the passing of a high-pressure front, and wind conditions were most suitable for several hours prior to the onshore breezes at sunrise. Suitable launch conditions were expected on only about fifty days through the winter period of maximum jet stream velocity, and the combined launch capacity of all three battalions was about 200 balloons per day.[17]

Gun cameras show balloons being shot down near the Aleutians

Initial tests took place in September 1944 and proved satisfactory; however, before preparations were complete, B-29s began their raids on the Japanese home islands. The attacks were somewhat ineffectual at first but still fueled the desire for revenge sparked by the Doolittle Raid.

The first balloon was released on November 3, 1944. Major Takada watched as the balloon flew upward and over the sea: "The figure of the balloon was visible only for several minutes following its release until it faded away as a spot in the blue sky like a daytime star." A few balloons carried radiosonde equipment rather than bombs. These balloons were tracked by direction finding stations in Ichinomiya, Chiba, in Iwanuma, Miyagi, in Misawa, Aomori, and on Sakhalin to estimate progress toward the United States.[18]

The Japanese chose to launch the campaign in November; because the period of maximum jet stream velocity is November through March. This limited the chance of the incendiary bombs causing forest fires, as that time of year produces the maximum North American Pacific coastal precipitation, and forests were generally snow-covered or too damp to catch fire easily. On November 4, 1944 a United States Navy patrol craft discovered one of the first radiosonde balloons floating off San Pedro, Los Angeles. National and state agencies were placed on heightened alert status when balloons were found in Wyoming and Montana before the end of November.[19]

The balloons continued to arrive in Oregon, Kansas, Iowa, British Columbia, Saskatchewan, Manitoba, Alberta, the Yukon, Northwest Territories,[1] Washington, Idaho, South Dakota, Nevada (including one that landed near Yerington that was discovered by cowboys who cut it up and used it as a hay tarp,[20] another by a prospector near Elko who delivered it to local authorities on the back of a donkey, and another was shot down by U.S. Army Air Forces planes near Reno). In all, seven fire balloons were turned in to the Army in Nevada, Colorado, Texas, Northern Mexico, Michigan, and even the outskirts of Detroit.[21] Fighters scrambled to intercept the balloons, but they had little success; the balloons flew very high and surprisingly fast, and fighters destroyed fewer than 20.

Through Firefly, the military used the United States Forest Service as a proxy agency to combat FuGo. Due to limited war time fire suppression personnel, Firefly relied upon the 555th as well as conscientious objectors. The operation also unified fire suppression communications among federal and state agencies. The influx of military personnel, equipment, and tactics shaped how the United States Forest Service approached fire suppression in the post War period.[23]

By early 1945, Americans were becoming aware that something strange was going on. Balloons had been sighted and explosions heard, from California to Alaska. Something that appeared to witnesses to be like a parachute descended over Thermopolis, Wyoming. A fragmentation bomb exploded, and shrapnel was found around the crater. A P-38 Lightning shot a balloon down near Santa Rosa, California; another was seen over Santa Monica; and bits of washi were found in the streets of Los Angeles.

On March 10, 1945, one of the last paper balloons descended in the vicinity of the Manhattan Project's production facility at the Hanford Site. This balloon caused a short circuit in the power lines supplying electricity for the nuclear reactor cooling pumps, but backup safety devices restored power almost immediately.[25]

Two paper balloons were recovered in a single day in Modoc National Forest, east of Mount Shasta. Near Medford, Oregon, a balloon bomb exploded in towering flames. The Navy found balloons in the ocean. Balloon envelopes and apparatus were found in Montana and Arizona, and inside Canada in Saskatchewan, in the Northwest Territories, and in the Yukon Territory. Eventually, an Army fighter managed to push one of the balloons around in the air and force it to ground intact, where it was examined and filmed. Japanese propaganda broadcasts announced great fires and an American public in panic, declaring casualties in the thousands.[26]

Hayfork is a small community in northern California about 40 miles (64 km) west of Redding. On February 1, 1945 a Japanese bombing balloon was spotted by several local residents drifting over the Trinity National Forest area and slowly descending. No one knew what it was, but an alert forest ranger called the military authorities at the Presidio of San Francisco and reported it. Meanwhile, the balloon came to rest atop a 60-foot (18-meter) dead fir tree in the forest near a local road. In the next few hours several people gathered in the area to gaze up at the strange object.

Shortly after dark there was a tremendous blast. The balloon's gas bag disappeared in a fireball and the balloon's undercarriage came crashing to the ground. No one was hurt. Forest rangers kept the curious well back from the fallen debris until Army personnel arrived. Upon examination, it was found to be a Japanese bombing balloon with four incendiary bombs and one high explosive bomb still aboard and the bomb releasing mechanism still very much intact. It later proved to be one of the most intact bombing balloons yet to fall into American hands. As was usual in instances of this sort, the local people were told what it was and were asked to keep secret what they had seen.[27]

Despite their low success, the authorities were worried about the balloons. There was the chance that they might get unlucky. Much worse, the Americans had some knowledge that the Japanese had been working on biological weapons, most specifically at the infamous Unit 731 site at Pingfan in northeast China, and a balloon carrying biowarfare agents could be a real threat.

Some of the sandbags dropped by the fusen bakudan were taken to the Military Geology Unit of the United States Geological Survey for investigation. Working with the Military Intelligence Service, the researchers of the Military Geological Unit began microscopic and chemical examination of the sand from the sandbags to determine types and distribution of diatoms and other microscopic sea creatures, and its mineral composition. The sand could not be coming from American beaches, nor from the mid-Pacific. It had to be coming from Japan. The geologists ultimately determined that the sand had been taken from the vicinity of Ichinomiya. Aerial reconnaissance then located two of the hydrogen production plants nearby, which were soon destroyed by bombing.[28]

The bombs caused little damage, but their potential for destruction and fires was large. The bombs also had a potential psychological effect on the American people. The U.S. strategy was to keep the Japanese from knowing of the balloon bombs' effectiveness.

In 1945 Newsweek ran an article titled "Balloon Mystery" in their January 1 issue, and a similar story appeared in a newspaper the next day.

The Office of Censorship then sent a message to newspapers and radio stations to ask them to make no mention of balloons and balloon-bomb incidents. They did not want the enemy to get the idea that the balloons might be effective weapons or to have the American people start panicking. Cooperating with the desires of the government, the press did not publish any balloon bomb incidents.[29] Perhaps as a result, the Japanese only learned of one bomb's reaching Wyoming, landing and failing to explode, so they stopped the launches after less than six months.

The press blackout in the U.S. was lifted after the first deaths to ensure that the public was warned, though public knowledge of the threat could have possibly prevented it.[29]

With no evidence of any effect, General Kusaba was ordered to cease operations in April 1945, believing that the mission had been a total fiasco. The expense was large, and in the meantime the B-29s had destroyed two of the three hydrogen plants needed by the project.

On May 5, 1945, a pregnant woman (Elsie Winters Mitchell, born February 26, 1919)[31] and five children were killed when they discovered a balloon bomb that had landed in the forest of Gearhart Mountain in Southern Oregon. Archie Mitchell was the pastor of the Bly Christian and Missionary Alliance Church. He and his pregnant wife Elsie drove up to Gearhart Mountain with five of their Sunday school students (aged 11–14) to have a picnic. They had to stop at this spot near Bly, Oregon, due to construction and a road closing. Elsie and the children got out of the car at Bly, while Archie drove on to find a parking spot. As Elsie and the children looked for a good picnic spot, they saw a strange balloon lying on the ground. There were two explosions; the boys were killed immediately, and Elsie died as Archie used his hands to extinguish the fire on her clothing. Joan Patzke survived the initial blast, but died later. A bomb disposal expert guessed that the bomb had been kicked.[32][33][34] These are the only known deaths caused by the balloon bombs. They are the only known deaths in the contiguous U.S. as the result of enemy action during World War II and the only civilian casualties on American soil after the US entry into the war.

Military personnel arrived on the scene within hours, and saw that the balloon still had snow underneath it, while the surrounding area did not. They concluded that the balloon bomb had drifted to the ground several weeks earlier, and had lain there undisturbed until found by the group.

Elsie Mitchell is buried in the Ocean View Cemetery in Port Angeles, Washington. A memorial, the Mitchell Monument, is located at the point of the explosion, 110 kilometers (68 miles) northeast of Klamath Falls in the Mitchell Recreation Area. It was listed in the National Register of Historic Places in 2001. Several Japanese civilians have visited the monument to offer their apologies for the deaths that took place here, and several cherry trees have been planted around the monument as a symbol of peace.[34]

The remains of balloons continued to be discovered after the war. Eight were found in the 1940s, three in the 1950s, and two in the 1960s. In 1978, a ballast ring, fuses, and barometers were found near Agness, Oregon, and are now part of the collection of the Coos Historical & Maritime Museum.[35]

^Ancona, Gaspar F. (2001). Where The Star Came to Rest. Strasbourg Cedex 2, France: Éditions du Signe. pp. 90–91. ISBN2-7468-0317-8. On January 23, 1945...It landed on the farm of Chris Stein near the intersection of 146th Avenue and 21st Street in northern Allegan County

"Balloons Of War" by John McPhee, The New Yorker, January 29, 1996, 52–60.

"Japan At War: An Oral History" by Haruko Taya Cook and Theodore F. Cook, New Press; Reprint edition (October 1993). Includes a personal account by a Japanese woman who worked in one of the fire balloon factories.